Unlicensed National Information Infrastructure (U-NII) devices are allowed to operate in 5.15-5.35 Gigahertz (GHz) and 5.725-5.825 GHz bands if they can perform Dynamic Frequency Selection (DFS) for preventing interference with radar operations.
Hardware of U-NII devices considers the identification of high-energy signals on which the receiver cannot identify the proper preamble for achieving the synchronization, as “synchronization errors.” Received radar signals do not have the U-NII preamble therefore they are reported by hardware as synchronization errors. But, interfering signals, as adjacent channel interference, interference from other systems operating in the same frequency, incorrectly received preamble due to temporary fading or due to interference from a hidden node, are also reported as synchronization errors. In order to perform a more detailed analysis for identifying the real source of the synchronization error, the U-NII hardware provide additional information as signal strength, signal length and the time of arrival of the interfering signal.
One important DFS requirement is that a U-NII device identifying radar signals in its operating frequency channel should move the operation to a different channel and should not return for at least thirty (30) minutes to the frequency channel where radar signals have been detected. In order to comply with this requirement and continue operating, U-NII devices should not only properly identify radar signals, but should also prevent interpretation of signals from other interfering sources as radar pulses. Practical operation has proven that devices, which cannot discriminate between radar pulses and interfering signals from other sources, would eliminate frequency channels one by one until the whole band is exhausted, as interference free channel does not practically exists.
Some radar detection algorithms are oriented on matching predefined pulses to the set of received signals. This approach has the disadvantage that it can identify only those patterns that have been described in advance. A second disadvantage of such algorithms is the fact that, for matching a large number of radar patterns, a large amount of computation has to be performed.
Accordingly, there is a need for a method and apparatus for accurate real time detection of short pulses radar signals
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.